For wood floors suitable for either residential or sports use, elongated, tongue and groove floorboards are generally used to provide an upper layer which has uniform structural characteristics and is aesthetically pleasing. Typically, the floorboards are strips of solid wood having a predetermined thickness. The strips are laid end to end in parallel rows, with the floorboards of each row interconnected via the tongue and the groove to the floorboards of adjacent rows. For structural stability, the ends of the floorboards of each row are staggered with respect to the ends of the floorboards of the adjacent rows. This structure forms an upper layer having a predetermined thickness, or vertical dimension, which is equal to the thickness of the individual floorboards. Floorboards may be of oak, maple, cherry or any other type of hardwood, or even of soft wood in some instances.
The overall cost of a wood floor system depends to a large extent on the cost of the wood components, and particularly the upper layer of floorboards. For the floorboards, cost generally increases with length. This characterization is general because it has proved neither practical nor cost effective for floor manufacturers to supply all solid floorboards of identical length, primarily because manufacturing operations require a finite number of sawing steps to be performed on boards of varying length. Requiring precise uniformity in length for all floorboards would increase overall costs, due to the inability to use the shorter end pieces. This would also increase the waste.
In recognition of these factors, and to assist manufacturers of floorboards in the pricing of floorboards, the Maple Flooring Manufacturer's Association (MFMA) has established criteria for grading the upper layer of a floor system in a manner which does not require exact uniformity in length for all boards. This criteria includes reference to length. For instance, top quality, or first grade, means that at least 50% of the floorboards are between 4' and 8' in length, though most are about 4.5', and only 10% are 15" or less. Second grade means that 20% of the floorboards may be 18" or less. Third grade means that up to 55% of the floorboards may be 18" or shorter.
While a floor system having an upper layer of shorter floorboards can function structurally as well as a floor system with an upper layer of longer floorboards, the shorter length of the floorboards does present some disadvantages, particularly with respect to installation. Staggering the ends of the floorboards of adjacently located rows takes longer because there are more pieces. Staggering can also present a problem if the upper layer is supported on spaced sleepers, since no single sleeper should be located below floorboard end joints of adjacently located rows.
Thus, in the wood floor system industry there has been a need to provide floorboards of uniform length and quality to facilitate the purchase and installation of reasonably priced floor systems. To this end, it is known in the industry to interconnect shorter pieces to form longer floorboards. One process used to form this interconnection is referred to as finger jointing, because fingers are sawed into the ends of the shorter pieces and the fingers are then interleaved to form a connected joint. Process and apparatus for finger jointing floorboards are disclosed in Goss U.S. Pat. No. 2,300,728; Malarky U.S. Pat. No. 2,334,113; Nicholson U.S. Pat. No. 2,908,600; Mann et al. U.S. Pat. No. 3,046,181; Gates U.S. Pat. No. 3,388,020; Cromeens et al. U.S. Pat. No. 3,927,705; and Maier U.S. Pat. No. 4,128,119.
While it is known in the industry to join relatively short floorboard pieces in end to end relationship via a finger jointed connection to form a longer floorboard, typical methods and apparatus for finger jointing floorboards often produce an upper layer which is not aesthetically pleasing, particularly if the floor surface must be sanded after installation. For a floorboard having an interleaved finger joint which extends the entire vertical dimension of the board, sanding the top or wear surface of the board may expose extended portions of the top fingers. If the two shorter boards are not joined precisely in the same longitudinal and transverse planes, as invariably occurs with typical, high tolerance finger jointing machines, sanding of the installed floorboards will expose uneven portions of the fingers, thereby exposing the horizontal unevenness of the finger jointed connection and resulting in an unsightly upper surface.
It is an object of this invention to improve upon the aesthetic appearance of a finger jointed floorboard which must be sanded after installation, without significantly increasing the cost of manufacture thereof.
It is another objective of the invention to reduce the amount of waste generated during the manufacture of floorboards used to form an upper layer of a floor system.
It is still another objective of this invention to maximize the utilization of relatively expensive floorboard resources in the manufacture and installation of a wood floor system having an aesthetically pleasing upper surface.